The invention described herein relates to optical parametric oscillators and more particularly to optical parametric oscillators in which the resonant radiation is separated from the input and output radiation within the cavity resonator.
The nonlinear response of parametric materials to incident radiation provides a useful technique for generating output wavelengths which are not otherwise readily attainable. Furthermore, by proper choice of the input radiation and parametric material and by various techniques for tuning the parametric output, a wide range of wavelengths may be produced. It is thus not surprising that these devices have aroused considerable interest as sources of coherent radiation for use in laser isotope separation processes. This is particularly true where radiation of the desired wavelength is not readily available from a primary laser.
Thus, for example, in laser separation of uranium isotopes using UF.sub.6 as the feed gas, it is highly desirable to obtain 16 .mu.m radiation to selectively excite those UF.sub.6 molecules containing a particular isotope of uranium. While it is known in the prior art that the requisite 16 .mu.m radiation could be achieved using a CdSe optical parametric oscillator operating on the 2.87 .mu.m input from an HF laser, significant problems exist with the prior art devices in obtaining sufficient output intensity and sufficiently narrow bandwidth of the output 16 .mu.m radiation. The problems associated with the prior art configurations are discussed in more detail in the section of this specification entitled "Optical Parametric Oscillation."